From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-17.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 00022C433E0 for ; Wed, 20 Jan 2021 18:52:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B8DAD206D4 for ; Wed, 20 Jan 2021 18:52:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392133AbhATSu7 (ORCPT ); Wed, 20 Jan 2021 13:50:59 -0500 Received: from mail.kernel.org ([198.145.29.99]:52766 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388578AbhATSl1 (ORCPT ); Wed, 20 Jan 2021 13:41:27 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 57C70233FA; Wed, 20 Jan 2021 18:40:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1611168046; bh=So2hXsCPM/a1uUQ14gqh3XEUn2Ub67sRlYHmUx5ZBnU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=PPGYkJ0O494qAN1VVylHGRuFEgw78KxA6AEpV+jVdxD1iP7SRb8OW3FUwWYE2+kxp +P+M98lH66kU0nErafFjuARB+RXT5jS0St/UILGmC0TZ59t6CarVkJeoBoPTw5sWhr bglU+5//FcGJm3ZGi3yve2Mo8M+VdEvgk8jP0DLwElsph9xmgUK9O0FECNDpuWc3Xp /XWHL2fVMj8y8zqRmHerPhcFqAb1u6onlJYWpRIgrJkTO3Hj6iazIww7T01SNWmgQw 00/pQpVo0KXxl97SAImC+mtFWMd7Tswp1tlBLFhxU3maLoiiNocuoh0KuszqfaeHZA 9bDg3jXWwTEzA== Received: by paulmck-ThinkPad-P72.home (Postfix, from userid 1000) id 267883522B82; Wed, 20 Jan 2021 10:40:46 -0800 (PST) Date: Wed, 20 Jan 2021 10:40:46 -0800 From: "Paul E. McKenney" To: "Uladzislau Rezki (Sony)" Cc: LKML , RCU , Michael Ellerman , Andrew Morton , Daniel Axtens , Frederic Weisbecker , Neeraj Upadhyay , Joel Fernandes , Peter Zijlstra , Michal Hocko , Thomas Gleixner , "Theodore Y . Ts'o" , Sebastian Andrzej Siewior , Oleksiy Avramchenko Subject: Re: [PATCH 1/3] kvfree_rcu: Allocate a page for a single argument Message-ID: <20210120184046.GE2743@paulmck-ThinkPad-P72> Reply-To: paulmck@kernel.org References: <20210120162148.1973-1-urezki@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210120162148.1973-1-urezki@gmail.com> User-Agent: Mutt/1.9.4 (2018-02-28) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 20, 2021 at 05:21:46PM +0100, Uladzislau Rezki (Sony) wrote: > For a single argument we can directly request a page from a caller > context when a "carry page block" is run out of free spots. Instead > of hitting a slow path we can request an extra page by demand and > proceed with a fast path. > > A single-argument kvfree_rcu() must be invoked in sleepable contexts, > and that its fallback is the relatively high latency synchronize_rcu(). > Single-argument kvfree_rcu() therefore uses GFP_KERNEL|__GFP_RETRY_MAYFAIL > to allow limited sleeping within the memory allocator. > > [ paulmck: Add add_ptr_to_bulk_krc_lock header comment per Michal Hocko. ] > Signed-off-by: Uladzislau Rezki (Sony) > Signed-off-by: Paul E. McKenney Queued all three for review and testing, thank you! Thanx, Paul > --- > kernel/rcu/tree.c | 42 ++++++++++++++++++++++++++---------------- > 1 file changed, 26 insertions(+), 16 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index e04e336bee42..2014fb22644d 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -3465,37 +3465,50 @@ run_page_cache_worker(struct kfree_rcu_cpu *krcp) > } > } > > +// Record ptr in a page managed by krcp, with the pre-krc_this_cpu_lock() > +// state specified by flags. If can_alloc is true, the caller must > +// be schedulable and not be holding any locks or mutexes that might be > +// acquired by the memory allocator or anything that it might invoke. > +// Returns true if ptr was successfully recorded, else the caller must > +// use a fallback. > static inline bool > -kvfree_call_rcu_add_ptr_to_bulk(struct kfree_rcu_cpu *krcp, void *ptr) > +add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp, > + unsigned long *flags, void *ptr, bool can_alloc) > { > struct kvfree_rcu_bulk_data *bnode; > int idx; > > - if (unlikely(!krcp->initialized)) > + *krcp = krc_this_cpu_lock(flags); > + if (unlikely(!(*krcp)->initialized)) > return false; > > - lockdep_assert_held(&krcp->lock); > idx = !!is_vmalloc_addr(ptr); > > /* Check if a new block is required. */ > - if (!krcp->bkvhead[idx] || > - krcp->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { > - bnode = get_cached_bnode(krcp); > - /* Switch to emergency path. */ > + if (!(*krcp)->bkvhead[idx] || > + (*krcp)->bkvhead[idx]->nr_records == KVFREE_BULK_MAX_ENTR) { > + bnode = get_cached_bnode(*krcp); > + if (!bnode && can_alloc) { > + krc_this_cpu_unlock(*krcp, *flags); > + bnode = (struct kvfree_rcu_bulk_data *) > + __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN); > + *krcp = krc_this_cpu_lock(flags); > + } > + > if (!bnode) > return false; > > /* Initialize the new block. */ > bnode->nr_records = 0; > - bnode->next = krcp->bkvhead[idx]; > + bnode->next = (*krcp)->bkvhead[idx]; > > /* Attach it to the head. */ > - krcp->bkvhead[idx] = bnode; > + (*krcp)->bkvhead[idx] = bnode; > } > > /* Finally insert. */ > - krcp->bkvhead[idx]->records > - [krcp->bkvhead[idx]->nr_records++] = ptr; > + (*krcp)->bkvhead[idx]->records > + [(*krcp)->bkvhead[idx]->nr_records++] = ptr; > > return true; > } > @@ -3533,8 +3546,6 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > ptr = (unsigned long *) func; > } > > - krcp = krc_this_cpu_lock(&flags); > - > // Queue the object but don't yet schedule the batch. > if (debug_rcu_head_queue(ptr)) { > // Probable double kfree_rcu(), just leak. > @@ -3542,12 +3553,11 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func) > __func__, head); > > // Mark as success and leave. > - success = true; > - goto unlock_return; > + return; > } > > kasan_record_aux_stack(ptr); > - success = kvfree_call_rcu_add_ptr_to_bulk(krcp, ptr); > + success = add_ptr_to_bulk_krc_lock(&krcp, &flags, ptr, !head); > if (!success) { > run_page_cache_worker(krcp); > > -- > 2.20.1 >